WASHINGTON – White House lawyer Ty Cobb is leaving President Trump's legal team, officials said Wednesday, as Trump jousts with special counsel Robert Mueller over the Russia investigation.

“For several weeks, Ty Cobb has been discussing his retirement, and last week, he let Chief of Staff (John) Kelly know he would retire at the end of this month," White House spokeswoman Sarah Sanders said.

Cobb, who is leaving less than a year after his appointment, said in a statement that "it has been an honor to serve the country in this capacity at the White House. I wish everybody well moving forward.”

Washington attorney Emmet Flood is slated to replace Cobb as the president's legal team, including former New York City mayor Rudy Giuliani, negotiates with Mueller about possible testimony from Trump and the possibility that the special counsel might subpoena the president.

Trump's legal team has almost completely turned over since the start of Mueller's investigation nearly a year ago.

John Dowd, one of the president's top private attorneys, left the case in late March.

The absence of Cobb may make Trump's testimony less likely; he had advocated that Trump at least provide written answers to Mueller's questions about suspected interference by Russia in the presidential election.

Dowd said Mueller talked about a possible subpoena for Trump if he refused to testify, though Trump's lawyers argued that the special counsel does not have the legal authority for such a step.

In an interview with ABC News, hours before the announcement of his retirement, Cobb said Trump's testimony is "certainly not off the table, and people are working hard to make decisions and work towards an interview."

"Ty has given us the benefit of some really great work," Giuliani said. "And Emmet Flood is a great replacement."

Giuliani, the chief negotiator with Mueller, said any interview of the president should not be longer than two or three hours, and questions should be limited.

A list of more than 40 questions Mueller would like to ask the president covers numerous aspects of the investigation, which is trying to determine whether there were links between Trump's 2016 presidential campaign and Russians who sought to intervene in the race in Trump's favor.

Mueller is also investigating whether Trump sought to obstruct justice in the inquiry, including by firing FBI Director James Comey a year ago.

Trump denied collusion and obstruction and described the investigation as a "hoax."

Cobb preached White House cooperation with Mueller and his investigators; his replacement could take a more confrontational approach.

The Failing New York Times purposely wrote a false story stating that I am unhappy with my legal team on the Russia case and am going to add another lawyer to help out. Wrong. I am VERY happy with my lawyers, John Dowd, Ty Cobb and Jay Sekulow. They are doing a great job and.....

I have agreed with the historically cooperative, disciplined approach that we have engaged in with Robert Mueller (Unlike the Clintons!). I have full confidence in Ty Cobb, my Special Counsel, and have been fully advised throughout each phase of this process.

Sanders said Flood would "represent the president and the administration against the Russia witch hunt."

Flood was part of the legal team that represented President Clinton during impeachment proceedings stemming from an investigation by special counsel Kenneth Starr that uncovered evidence that Clinton had an extramarital relationship with White House intern Monica Lewinsky.

Beyond the Cobb job, Flood is also being considered as an eventual replacement for White House Counsel Don McGahn should he decide to leave, officials said.

Cobb said that his primary responsibility was document production and that all pertinent records were turned over to the special counsel.

"I have agreed with the historically cooperative, disciplined approach that we have engaged in with Robert Mueller (Unlike the Clintons!)," Trump tweeted April 12. "I have full confidence in Ty Cobb, my Special Counsel, and have been fully advised throughout each phase of this process."

On March 11, Trump tweeted criticism of a New York Times story that said he was unhappy with his legal team. "Wrong," he said. "I am VERY happy with my lawyers, John Dowd, Ty Cobb and Jay Sekulow. They are doing a great job."

Two months later, Sekulow remains, Dowd has left, and Cobb is leaving.